早发性帕金森病患者线粒体DNA部分点突变的研究

目的　验证线粒体DNA点突变与早发性帕金森病 (PPD)的相关性 ,并了解中国人线粒体DNA点突变特点。方法　用聚合酶链反应 (PCR)、斑点杂交、放射显影定性方法对 4 0例PPD患者及 4 8名健康对照组A4 336C、G5 4 6 0A、A10 398G、A13780G突变点进行检测 ,对 2 0例PPD组和 2 0例对照组碱基位点 10 2 5 6～ 10 5 77线粒体DNA片段测序。结果　PPD组A10 398G、G5 4 6 0A、A4 336C、A13780G ,4个位点的突变率均高于对照组 ,而且PPD组A10 398G突变率 (5 0 0 % )显著高于对照组 (14 6 % ) (P =0 0 0 0 1) ;其他 3个突变点PPD组的突变率与对照组比较差异无显著意义 ;新发现碱基位点 10 4 0 0C/T多态性。结论　线粒体DNA突变与PPD的发病存在相关性 ,A10 398G突变很可能是PPD发病的一个重要原因 ;中国人线粒体DNA存在 10 4 0 0C/T多态性和PPD患者A10 398G高突变率 (5 0 0 % )特点     

线粒体 DNA 与阿尔茨海默病的关系

阿尔茨海默病(AD)是最常见的与痴呆有关的神经退行性疾病。已证实家族聚集性 AD与淀粉样前体蛋白基因及早老素1、早老素2基因的突变有关,而迄今为止,仍未发现与散发性 AD 相关的致病基因。研究表明,线粒体 DNA(Mitochondrial DNA,mtDNA)突变可导致能量代谢障碍、氧化应激增多以及β淀粉样蛋白的积累,进而导致 AD 的发生、发展。然而,关于 mtDNA 突变或单倍群与 AD关系的研究结果是有争议的。现对 mtDNA 与 AD 的关系进行综述,以期指导后续研究。     

线粒体DNA修复系统与神经疾病

Clayton曾报道线粒体不能清除粒体DNA(i mtochondri-cal DNA,mtDNA)中由紫外钱诱导生成的嘧啶二体,因而一直认为线粒体没有mtDNA修复功能。近年来,通过对原核生物和低等真核生物的研究,人们对DNA修复系统有了深入的认识,证明mtDNA修复系统可保持mtDNA遗传物质的完整性和稳定性,避免遗传物质突变的产生,保证DNA复制的高保真度。但是对其仍缺乏完整的理解。目前报道在线粒体中存在碱基切除修复、错配修复、重组修复、直接修复等修复系统。较多研究证实mtDNA修复系统与一些神经疾病发病相关。1线粒体DNA(mtDNA)基因组结构及其修…     

阿尔茨海默病与线粒体辅酶Ⅱ基因的关系

目的：探讨阿尔茨海默病（AD）与线粒体的细胞色素氧化酶亚基Ⅲ（COX3）和辅酶Ⅱ（ND2）基因突变的关联性。方法：采用聚合酶链反应-限制性片段长度多态性技术,检测符合国际疾病分类第10版（ICD-10）诊断标准的60例AD患者（患者组）,10个AD家系,和60名正常老人（对照组）的基因型和基因频率。结果：患者组线粒体ND2的nt5460基因位点基因变异为G→A,变异率13.3%,家系中同时有基因变异G→A,但变异无统计学意义。患者组中线粒体COX3的nt9861基因位点无基因变异。患者组和对照组均未发现基因有T→C的变异。结论：AD患者很有可能存在ND2的nt5460位点发生G→A的基因突变,与COX3的nt9861位点T→C突变无关。     

线粒体脑肌病伴高乳酸血症和卒中样发作综合征与一种新的线粒体DNA基因突变

目的 检测1例线粒体脑肌病伴高乳酸血症和卒中样发作综合征(MELAS)患者脑组织和外周血线粒体DNA(mtDNA)的基因突变类型。方法 应用聚合酶链反应-限制性片段长度多态性(PCR—RFLP)方法对这例MELAS患者脑组织和外周血mtDNA的A3243G点突变进行检测，对检测过程中发现的异常扩增产物进行DNA测序分析。结果 该例MELAS患者脑组织和外周血白细胞PCR扩增产物行聚丙烯酰胺凝胶电泳时产生了两条带，一条为494bp，另一条为218bp。494bp的扩增产物是目的片段，而218bp的片段是一种异常扩增产物。我们对218bp的PCR扩增产物进行测序，发现在mtDNA3314—3589之间有276bp的碱基缺失。结论 mtDNA3314-3589位点之间276bp的碱基缺失可能是导致MELAs的一种新的基因突变类型。     

线粒体基因突变与脑胶质瘤的发生

脑胶质瘤是一种极具侵袭性的神经系统常见恶性肿瘤,虽然其发病机理尚不完全明确,但普遍认为其发生和发展是多个癌基因过度表达和抑癌基因失活的结果。近年来,脑胶质瘤发生的研究主要集中于核基因突变。作为高等动物细胞内唯一的核外DNA,线粒体DNA（mitochondrial DNA,mtDNA）突变在肿瘤发生中的作用也逐渐受到关注。随着对线粒体及其DNA研究的日益深入,人们发现线粒体结构和功能的改变以及mtDNA突变不仅与多种疾病的发生有关,而且在肿瘤发生过程中也可能发挥一定的作用。     

单纤维PCR技术检测线粒体DNA的突变

单纤维PCR技术在单细胞水平研究线粒体DNA(mitochondrialDNA,mtDNA)的突变,不仅能确定线粒体肌病与脑肌病患者骨骼肌是否存在线粒体DNA突变及其类型,还能研究线粒体DNA突变类型和突变比例与骨骼肌病理改变的相互关系,认识线粒体基因型与表型的对应关系。线粒体是细胞的“能     

粒脑肌病伴高乳酸血症和卒中样发作患者的临床、病理和线粒体DND突变分析

目的 能量代谢障碍是青年期卒中的重要病因之一,该研究总结线粒体脑肌病伴高乳酸血症和卒中样发作(mitochondrial encephalomyopathy with lactic acidosis and stroke-like episode.MELAS)患者的临床,病理特征,分析线拉体DNA突变,望能有助于提高对该病的认识、改进青年卒中的诊治.方法 回顾分析15例临床特征和骨骼肌病理符合MELAS的患者.分析线粒体脱氧核糖核酸(mitochondrial DNA,mtONA)突变,多聚酶链反应(polymerase chain reaction,PCR)后直接测序分析mtDNA热点突变,并对未发现热点突变的患者进行全mtDNA序列分析.结果 15例患者的临床表现以头痛和卒中样发作,癫癎发作为主要表现,病灶以皮层尤其枕叶、顶叶为多,磁共振成像(magnetic resonance imaging,MRI)有一定特征,生化检查发现血乳酸、乳酸/丙酮酸此值升高,肌酶轻度升高,病理上以破碎红纤维(ragged-red fibers,RRF)和细胞色素C氧化酶(cytochrome C oxidase,COX)/琥珀酸脱氲酶(Succinate dehydrogenase,SDH)蓝染纤维为主要特征,电镜下显示线粒体增多,线拉体内包涵体.11例由亮氨酸转运核搪核酸(mitochondrial tRNA for leucine,MTTL1,tRNA1)基因突变导致,细胞色素C氧化酶亚单位3(Cytochrome c oxidase subunit 111,C05)基因9469C/T突变,线粒体ATP合成酶亚单位8(Subunit 8 of mitochondrial ATP synthase.ATP8)基因8469A/G突变和细胞色素C氧化酶亚单位1(Cytochrome c oxidase subunit 1,C01 or MTC01)基因62553T/C突变各1例,1例患者无任何mtDNA突变.结论 MELAS是青年期卒中重要原因之一,肌肉活检是临床诊断的主要手段,mtDNA突变分析尤其是热点突变(MTTL1,5245G和MTTL1*5271C)分析对于确诊有重要价值.     

细胞色素C氧化酶1基因T6253C点突变致线粒体脑肌病伴有高乳酸血症和卒中样发作综合征一例

目的报道1例33岁男性，头痛后继以卒中样发作，影像学提示基底节区和颞枕叶缺血性改变，肌肉活检证实线粒体结构和功能异常的患者的基因突变。方法我们应用基因分析未发现常见致病性突变，因此应用DNA芯片扫描线粒体基因全序列，寻找可能的致病突变。通过DNA芯片扫描线粒体基因全序列，应用直接测序法证实突变。结果在线粒体DNA共发现了3个新突变，其中T6253C突变导致细胞色素C氧化酶1第117位保守的蛋氨酸被苏氨酸取代，患者的母亲也携带相同的突变，而98名健康个体无人携带此突变，我们认为T6253C是导致该患者发病的致病突变。结论这是首例关于细胞色素C氧化酶1基因点突变导致线粒体脑肌病伴有高乳酸血症和卒中样发作综合征的报道。     

Alzheimer病线粒体DNA突变分子生物学研究进展

脑能量代谢降低为AD发病的危险因素之一 ,而线粒体是细胞能量储存和供给的重要场所。近年研究认为 ,线粒体DNA突变与AD的发病有关 ,本文就线粒体DNA突变在AD发病中的致病作用予以综述     

Mitochondrial DNA A4336G mutation in Alzheimer's and Parkinson's diseases

OBJECTIVES: To determine whether the mitochondrial DNA (mtDNA) A4336G mutation represents a risk factor for Spanish patients with both Alzheimer's disease (AD) and Parkinson's disease (PD). MATERIAL AND METHODS: One hundred and sixty-one AD and 106 PD unrelated patients were included in the study. Seventy-eight age-matched and 144 randomly chosen healthy subjects served as controls. The frequency of the A4336G mutation in these groups was compared using the chi(2) and Fisher's exact tests. p < 0.05 was established as a statistically significant differential value. RESULTS: The mtDNA A4336G mutation was present in 1/161 of AD patients (0.6%), in 3/106 of PD patients (2.8%), in 1/78 of age-matched controls (1.3%) and in 2/144 of the randomly chosen controls (1.4%). These differences were not statistically significant. CONCLUSION: Our results do not support the hypothesis that this mutation represents a risk factor for either AD or PD patients, at least in the case of this Spanish sample.     

Mitochondrial DNA haplogroups and susceptibility to AD and dementia with Lewy bodies

ARTICLE ABSTRACT: The authors analyzed the relationship between nuclear genetic risk factors (apolipoprotein E genotype) and mitochondrial DNA (mtDNA) sequence variants in pathologically proved cases of AD (n = 185), dementia with Lewy bodies (DLB; n = 84), and control subjects (n = 179). Specific European mtDNA haplogroups and the A4336G mutation were not associated with an increased risk of AD. mtDNA haplogroup H was overrepresented in the DLB patients when compared with control subjects. Additional studies are needed to clarify the significance of the association.     

Mitochondrial DNA mutations in complex I and tRNA genes in Parkinson's disease

OBJECTIVE: To identify mitochondrial DNA (mtDNA) mutations that predispose to PD. BACKGROUND: Mitochondrial complex I activity is deficient in PD. mtDNA mutations may account for the defect, but the specific mutations have not been identified. METHODS: Complete sequencing was performed of all mtDNA-encoded complex I and transfer RNA (tRNA) genes in 28 PD patients and 8 control subjects, as well as screening of up to 243 additional PD patients and up to 209 control subjects by restriction digests for selected mutations. RESULTS: In the PD patients, 15 complex I missense mutations and 9 tRNA mutations were identified. After screening additional subjects, rare PD patients were found to carry complex I mutations that altered highly conserved amino acids. However, no significant differences were found in the frequencies of any mutations in PD versus control groups. The authors were unable to confirm previously reported associations of mutations at nucleotide positions (np) 4336, 5460, and 15927/8 with PD. Complex I mutations previously linked to Leber's hereditary optic neuropathy, one of which has been linked to atypical parkinsonism, were not associated with PD. CONCLUSIONS: mtDNA mutations with a high mutational burden (present in a high percentage of mtDNA molecules in an individual) in complex I or tRNA genes do not play a major role in the risk of PD in most PD patients. Further investigations are necessary to determine if any of the rare mtDNA mutations identified in PD patients play a role in the pathogenesis of PD in those few cases.     

Mitochondrial DNA variants in a portuguese population of patients with Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder associated with dementia in late adulthood. Mitochondrial respiratory chain impairment has been detected in the brain, muscle, fibroblasts and platelets of AD patients, indicating a possible involvement of mitochondrial DNA (mtDNA) in the etiology of the disease. Several reports have identified mtDNA mutations in AD patients, but there is no consensual opinion regarding the cause of the impairment. We have studied mtDNA NADH dehydrogenase subunit 1 nucleotides 3337-3340, searching for mutations. Our study group included 129 AD patients and 125 healthy age-matched controls. We have found alterations in two AD patients: one had two already known mtDNA modifications (3197 T-C and 3338 T-C) and the other a novel transition (3199 T-C) which, to our knowledge, has not been described before.     

Association of the mitochondrial tRNAA4336G mutation with Alzheimer's and Parkinson's diseases

Alzheimer's and Parkinson's diseases (AD, PD) are among the most common neurodegenerative disorders in adults. Both AD and PD have a complex aetiology, and it is widely considered that genetic factors, acting independently or in concert with other genetic and/or environmental factors, modify the risk of developing them. While the apolipoprotein E (ApoE) ε4 allele represents an established risk factor for familial and sporadic late‐onset AD, it has been suggested that a common polymorphism in the α1‐antichymotrypsin gene modifies the ApoE ε4 dosage effect in AD. Moreover, it has been proposed that a mitochondrial tRNA^Gln sequence variant (A4336G transition) confers an increased risk for both AD and PD. This finding is of particular interest as the A4336G mutation seems to predispose to two clinically and neuropathologically distinct neurodegenerative disorders. We have examined the allelic frequencies of these putative susceptibility genes in 28 neuropathologically confirmed cases of AD, 23 cases with Lewy‐body PD and 100 age‐matched controls without clinical or histological evidence of neurodegenerative disease. The ApoE ε4 allele frequency was significantly over‐represented in AD patients vs controls (0.35 vs 0.11) but we could not find evidence for an association between the α1‐antichymotrypsin AA genotype, the ApoE ε4 allele and AD. In contrast, the mtDNA^A4336G mutation was present in one of 28 AD cases and in two of 23 PD patients, whereas no mutation was found in 100 age‐matched controls ( P <0.05). Our data therefore support the hypothesis that the mitochondrial A4336G mutation represents a risk factor for AD and PD.     

Complex I polymorphisms, bigenomic heterogeneity, and family history in Virginians with Parkinson's disease

The electron transport chain enzyme complex I may play a role in Parkinson's disease (PD) pathogenesis. Association studies considering whether or not complex I-relevant gene polymorphisms contribute to PD risk are discordant. We evaluated four complex I-relevant gene polymorphisms alternatively reported to associate and not associate with PD (tRNA(Gln) T4336C, ND1 T4216C, ND2 G5460A, and the NDUFV2 exon 2 C182T transition). Our study included 111 PD subjects and 106 controls in central Virginia. Individuals with at least one copy of the NDUFV2 182T allele were more likely to report a PD family history than non-carriers, but aside from this no positive associations were found. Indeed, the tRNA(Gln) 4336C variant occurred more frequently in controls. We also observed that individuals in both groups often carried more than one of the assayed polymorphisms, and for the first time show bigenomic polymorphic variation (between nuclear and mtDNA complex I subunit genes) commonly occurs within individuals. In an exploratory sub-analysis, more control than case women had an ND1 4216C, NDUFV2 homozygous 182C compound genotype. Complex I compound genotype variation commonly occurs and may explain why particular complex I gene polymorphisms associate with PD in some populations but not others.     

The influence of nuclear background on the biochemical expression of 3460 Leber's hereditary optic neuropathy

The role of mitochondrial DNA (mtDNA) mutations in the pathogenesis of Leber's hereditary optic neuropathy (LHON) has yet to be characterized. Several clinical feature of the disease imply that nuclear genes might also be involved in its expressions. We have confirmed the presence of a severe NADH:coenzyme Q₁ reductase (complex I) defect in association with the A3460G mtDNA LHON mutation in cultured fibroblasts compared with age-matched controls. This defect was not seen in clonal fibroblasts with 0% mutant mtDNA developed from a heteroplasmic A3460G LHON subject, confirming the association between the A3460G mutation and the complex I defect. Cybrids prepared from the fusion of enucleated fibroblasts homplasmic for the A3460G mutation with 206 (osteosarcoma) cells lacking mtDNA (ρ^o) also had a severe deficiency of complex I activity. However, in A3460G LHON fusion cybrids containing a different nuclear background, A549 ρ^O (lung derived), this biochemical defect was not apparent in all the clones studied. These results suggest that the nuclear environment can influence the expression of the biochemical defect in LHON patients with the A3460G mutation.     

Common mitochondrial DNA and POLG1 mutations are rare in the Chinese patients with adult-onset ataxia on Taiwan

BACKGROUND AND PURPOSE: Spinocerebellar ataxia (SCA) is a heterogeneous group of neurodegenerative disorders with common features of adult-onset cerebellar ataxia. Many patients with clinically suspected SCA are subsequently diagnosed with common SCA gene mutations. Previous reports suggest some common mitochondrial DNA (mtDNA) point mutations and mitochondrial DNA polymerase gene (POLG1) mutations might be additional underlying genetic causes of cerebellar ataxia. We tested whether mtDNA point mutations A3243G, A8344G, T8993G, and T8993C, or POLG1 mutations W748S and A467T are found in patients with adult-onset ataxia who did not have common SCA mutations. METHODS: Four hundred seventy-six unrelated patients with suspected SCA underwent genetic testing for SCA 1, 2, 3, 6, 7, 8, 10, 12, 17, and DRPLA gene mutations. After excluding these SCA mutations and patients with paternal transmission history, 265 patients were tested for mtDNA mutations A3243G, A8344G, T8993G, T8993C, and POLG1 W748S and A467T mutations. RESULTS: No mtDNA A3243G, A8344G, T8993G, T8993C, or POLG1 W748S and A467T mutation was detected in any of the 265 ataxia patients, suggesting that the upper limit of the 95% confidence interval for the prevalence of these mitochondrial mutations in Chinese patients with adult-onset non-SCA ataxia is no higher than 1.1%. CONCLUSIONS: The mtDNA mutations A3243G, A8344G, T8993G, T8993C, or POLG1 W748S and A467T are very rare causes of adult-onset ataxia in Taiwan. Routine screening for these mutations in ataxia patients with Chinese origin is of limited clinical value.     

Investigation on mtDNA deletions and twinkle gene mutation (G1423C) in Iranian patients with chronic progressive external opthalmoplagia

BACKGROUND: Chronic progressive external ophthalmoplagia (CPEO) is a phenotypic mitochondrial disorder that affects external ocular and skeletal muscles and is associated with a single or multiple mitochondrial DNA (mtDNA) deletions and also nuclear gene mutations. There are also some reports about the relationship between CPEO and the nuclear Twinkle gene which encodes a kind of mitochondrial protein called Twinkle. AIMS: To study the mtDNA deletions and Twinkle gene G1423C point mutation in Iranian patients with CPEO. MATERIALS AND METHODS: We collected 23 muscle samples from patients with CPEO, 9 women (mean age 34.3 years) and 14 men (36.7 years). Multiplex polymerase chain reaction (PCR) method was used to find the presence of single or multiple deletions in mtDNA. Single stranded conformational polymorphism (SSCP) and restriction fragment length polymorphism (PCR-RFLP) methods were carried out to investigate point mutation (G1423C) in the Twinkle gene in all DNA samples. RESULTS: Different sizes of mtDNA deletions were detected in 16 patients (69.6%). Each of the 5.5, 7, 7.5 and 9 kb deletions existed only in 1 patient. Common deletion (4977bp) and 8 kb deletion were detected in 5 and 3 patients respectively. Multiple deletions were also present in 4 patients. Out of 23 patients included in our study, two cases (8.7%) had Twinkle gene mutation (G1423C) and 5 patients (21.7%) did not show any deletions in mtDNA or the Twinkle gene mutation. CONCLUSION: Our study provides evidence that the investigation of mtDNA and Twinkle gene mutations in CPEO may help with early diagnosis and prevention of the disease. Patients who did not show deletions in the mtDNA or G1423C mutation in the Twinkle gene may have other mtDNA, Twinkle or nuclear gene mutations.     

Novel cluster of tRNALeu(UUR) mutations in a sporadic case of infantile myopathy restricted to muscle tissue

In a previous study we reported on a case with severe infantile, mitochondrial myopathy caused by somatic mutation [12]. In the present study we give evidence for asymmetric tissue distribution of the mutations. Mitochondrial DNA (mtDNA) analysis showed a cluster of nearly homoplasmic point mutations in the tRNA gene for leucine (UUR) (A3259 G, A3261 G, A3266 G, A3268 G). The mutation is abundant in muscle, but is not found in blood cells. This cluster of mutations is sporadic, because the search for mutant molecules in the blood of the healthy mother and maternal grandmother did not show these alterations.